1. Field of the Invention
The present invention generally relates to steam boilers and more specifically, the apparatus for determining the existence of fluid leaks from pressurized tubing suspended within a boiler combustion space.
2. Description of the Prior Art
To detect the existence of steam leaks from boiler tubes suspended within a combustion space, acoustically sensitive systems have been developed to monitor combustion chamber sound emissions. Such systems are designed to measure the magnitude of sonic energy from the combustion chamber over a narrow frequency spectrum distinctive to fluid leaks from conduits.
Essential to such acoustic systems are one or more pressure transducers or microphones tuned to the frequency spectrum of greatest interest. In deference to the fact that transducer materials are heat sensitive, or, at least unable to withstand direct combustion chamber conditions, these transducers must be physically positioned in wave guides outside the combustion chamber walls.
Wave guides are tubular conduits of about 11/2 to 2 inches diameter having polished internal bores. An open end of the conduit penetrates the combustion chamber wall to be aimed at a precise boiler tube section. The other or external end of the wave guide conduit, whereat the sonic pressure transducer is mounted, is closed to provide an insular dead air space between the transducer and the direct combustion environment. Frequently, the wave guide conduit is arced up to 90 degrees along the tubular axis.
Although the wave guide dead air space effectively insulates a sonic transducer from heat, the open bore of the wave guide tube at the combustion chamber end thereof is vulnerable to an accumulation of combustion products collectively characterized as "soot." If permitted, soot will deposit within the wave guide bore until complete plugging occurs. Any substantial accumulation will reduce the sonic transmission efficiency of the guide. Keeping such wave guide bores clear of soot is therefore a substantial maintenance burden: especially in the case of chemical recovery boilers which generate soot at rates several times greater than traditional fuel fired boilers.
In the past, soot clearing maintenance has been served by an external rodding port axially aligned with the wave guide bore opening. Although such ports provide convenient manual accessibility to the critical soot accumulation areas, the task remains as basically manual function. For an acoustic leak detection system utilizing 12 or more transducers and wave guides as primary data sources, such manual maintenance represents a substantial labor burden.
It is, therefore, an object of the present invention to provide an acoustic detection unit for boilers having minimum manual maintenance requirements.
Another object of the invention is to provide an automatic soot clearing system for acoustic detection wave guides.